1. Field of the Invention
The present invention relates to a clutch bearing assembly which engages upon torque being applied by an input member when rotating in one direction, and acting as a rolling element anti-friction bearing when the input member rotates in the opposite direction. More specifically, the present invention relates to a one-way clutch assembly of a roller/ramp variety and the mechanism by which rollers are retained and biased in the assembly.
2. Description of the Prior Art
One-way clutch bearing assemblies are used in a wide variety of applications. One possible application is use in a paper copier or other low torque applications. During operation of a copier, it is often desirable to disconnect the drive shafts or rollers of the copier from the drive train. When disconnected, the paper feeding shafts can rotate freely with respect to the drive train and, accordingly, they are free to rotate with regard to the speed of the drive train. At other times, it is preferred that the paper feeding elements of the copiers automatically lock to the drive train whenever there is a relative disproportional rotation between the paper drive rollers and the input member from the drive train. The above mentioned clutch assemblies have also been provided where a clutch assembly transfers torque in two directions and where the torque can be transferred in two directions.
In one type of clutch assembly, concentric driving and driven members are provided with a driving member having axial surfaces which face toward another member. Upon each surface, a roller is loosely held. The assemblies are referred to as roller/ramp clutch assemblies. The rollers are initially responsive to acceleration of the driving member and when the rotational acceleration of the driving member occurs, the inertia of the rollers causes them to move along the surfaces toward a side edge of the surfaces. At the side edge, the distance between the surfaces and the driven member is less than the diameter of the roller and the roller contacts the driven member, becoming engaged or locking in the wedge fault between the axial surfaces of the drive member and the circumference of the driven member. In some varieties, the rollers can move along the axial surface to either side. In other types, the engagement of the driven member is only possible by movement of the roller to one side of the surface.
In the later systems, however, complex mechanisms are used to retain the rollers into the grooves. The mechanisms have also generally failed to ensure that the rollers will engage between the driving and driven members at the same time. Failure to provide simultaneous engagement results in disproportionate stresses being applied to the rollers, the driven members, and the driving member. Additionally, non-simultaneous engagement of the rollers has the effect of making the engagement and disengagement more noticeable during the operation of the copier or other device.
Prior designs of roller/ramp clutch assemblies have also used a common biasing member to bias all of the rollers to their non-engaged positions. As a result, greater biasing forces are required and the failure of the biasing member results in the assembly functioning improperly. It is the later type of assembly that the present invention particularly relates.
In view of the foregoing limitations and shortcomings of the prior art devices, as well as other disadvantages not specifically mentioned above, there exists a need in the art for an improved roller/ramp clutch assembly. The primary object of the current invention is to provide a one-way clutch which is relatively simple in construction and yet has both the function of a one-way clutch and the function of a roller bearing. Therefore, as compared to the conventional arrangement using a separate radial bearing, the inventive arrangement achieves decreases in axial dimension, weight and cost, and is suitable particularly for applications having limitations of size, weight and cost. Further, standard bearing rings can be used as the inner and outer members either intact or by applying more or less processing thereto; which is very advantageous from the standpoint of cost.
Briefly described, these and other objects are accomplished according to the present invention by providing a one-way clutch assembly having a roller/ramp design. The assembly includes independently rotatable inner and outer bearing race members, either of which can function as a driving or driven members. The races are opposing cylindrical surfaces, are concentric about a central axis, and define a gap therebetween.
Formed in at least one of the cylindrical surfaces is a raceway for receiving the rolling elements, in this case ball elements.
Located between the inner and outer races are a plurality of ball elements, each ball element being located within the bearing raceway. A series of segmented retainers are circumferentially disposed between the ball elements so that they can all rotate about a central axis independently of the other ball elements. A connector circumferentially interconnects all of the retainers so that they can rotate about a central axis independently of the inner and outer races. By utilizing the connector, the retainers can all substantially move circumferentially in unison and, therefore, the ball elements can engage and disengage between the members in unison.
The segmented retainers feature a xe2x80x9cUxe2x80x9d shaped open groove, which forms a pair of ramps for engaging an adjacent ball element when the relative rotation between race members is in one direction. As the rollers or bearings move up the ramps, the segmented retainer and the engaging ball elements wedged between the races. This action results in torque being transferred between the inner and outer race members. This can be used as a brake when one race member is coupled to a ground structure, or to transfer rotational torque to another machine element. The ball elements are also independently biased by the connector element which is coupled to the rotating segmented retainers. In one embodiment, the biasing is provided by resilient tabs that engage the surface of the ball elements. In another embodiment, the ball elements are biased by engagement with the supported segmented retainer.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and dependent claims, taken in conjunction with the accompanying drawings.